Update requirements pls so that it can be used with "zammad/zammad-api-client-php": "2.0.*"

[skalec]

Root composer.json requires muhammadn/laravel-zammad ^0.0.10 -> satisfiable by muhammadn/laravel-zammad[0.0.10].
- muhammadn/laravel-zammad 0.0.10 requires zammad/zammad-api-client-php ^1.2 -> found zammad/zammad-api-client-php[1.2.0, ..., 1.6.1] but it conflicts with your root composer.json require (2.0.*).

[muhammadn]

@skalec If you can create a PR for this that would be great! it's pretty trivial to use this (maybe lesser more than 1.2 but lesser than 3 should be good!)